Please refer to FIG. 1. FIG. 1 is a schematic diagram of an optical recording system 10 according to the prior art. The optical recording system 10 comprises a pickup head 12 and an optical recording media 14. The optical recording media 14 comprises a spiral recording track 16, a series of indents. The pickup head 12 reads data on the track 16 by locking onto the track 16 of the optical recording media 14.
The pickup head 12 has to read the data in different positions on the optical recording media 14. Because the pickup head 12 can only move in a radial direction on the optical recording media 14, the pickup head 12 can not move directly from position A to position C. Therefore, the pickup head 12 has to move from position A to position B and then from position B to position C to lock onto the track 16 again and reads the data on position C.
Though, the optical recording media 14 has only one spiral-recording track 16. When the pickup head 12 moves from position A to position B, the pickup head 12 seems to across a number of recording tracks. The movement form position A to position B is called seek or seeking. After seeking, the pickup head 12 has to move from position B to position C to lock onto a target track again and then reads data on the target track. The movement from position B to position C is called following.
After seeking, the optical recording system 10 exerts brake force to make the pickup head 12 stop before switching to the following. When the pickup head 12 is seeking, the pickup head 12 is going to stop slowly, but the velocity of the pickup head 12 is still fast and the momentum of the pickup head 12 is still strong. It is difficult for the pickup head 12 to lock onto the next target track immediately. Therefore, the optical recording system 10 has to exert brake force on the pickup head 12 for making the pickup head 12 stop before switching to the following.
After seeking and before switching to the following, the optical recording system 10 exerts brake force to make the pickup head 12 stop. Before the pickup head 12 finishes seeking, an estimating mechanism of control IC of the pickup head 12 informs the pickup head 12 that how far the target-recording track is. The optical recording system 10 exerts brake force when the last (or the last half of) track arrives. The prior art used a fixed brake force. It cannot smoothly decrease the velocity of the pickup head under many circumstances.
The optical recording system 10 breaks the pickup head with the fixed brake force. If the final velocity of the pickup head 12 is fast, the optical recording system 10 spends a long time to brake the pickup head 12 and the pickup head 12 will exceed the target recording track. If the final velocity of the pickup head 12 is slow, the optical recording system 10 spends a short time to brake the pickup head 12 and the pickup head 12 will not arrive at the target recording track. Therefore, the optical recording system 10 has to make the pickup head 12 lock onto the target recording track by following.